Phytoplankton are responsible for roughly half of global annual primary production; however, the magnitude of that contribution varies orders of magnitude across ocean providences. From the gyres that are dominated by picoplankton to the high nutrient upwelling zones, phytoplankton community composition and physiology play an important role in setting the magnitude and pace of primary production. I am interested in the different pressures that shape phytoplankton communities and physiology and, in turn, how different communities alter biogeochemical cycles.
Silicon and diatoms Diatoms are an immensely diverse and highly productive group of phytoplankton. They are unique among phytoplankton in their use of silicon to create ornate frustules (cell walls) of silica. I developed a quantitative method using the fluorescent dye, PDMPO, to measure single diatom cell silica production rate, growth rate and silicification (frustule thickness) in natural diatom assemblages. Using this method, we have started to look at how community composition influences silicon cycling and how silicon limitation affects diatom physiology. Below are pictures of diatoms that have been labeled with PDMPO from the California Current.
Microzooplankton and the Carbon Cycle My current research is aimed at the role of microzooplankton herbivory in export processes of the biological pump as part of the NASA Exports mission. Analysis is underway for experiments from the recent cruise to the North Pacific, stay tuned for updates.